Ultrasonic transducer, ultrasonic transducer array, and ultrasonic device

ABSTRACT

An ultrasonic transducer is configured to transmit or receive ultrasonic waves. The ultrasonic transducer includes a vibrating member and a piezoelectric member coupled to the vibrating member. The piezoelectric member includes a first piezoelectric part configured and arranged to be deformed by applied voltage to vibrate the vibrating member or configured and arranged to be deformed by vibration of the vibrating member to produce a potential difference, and a second piezoelectric part configured and arranged to be deformed by applied voltage to statically deflect the vibrating member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2008-320954 filed on Dec. 17, 2008 and Japanese Patent Application No.2009-244429 filed on Oct. 23, 2009. The entire disclosures of JapanesePatent Application Nos. 2008-320954 and 2009-244429 are herebyincorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to an ultrasonic transducer, ultrasonictransducer array, and ultrasonic device.

2. Related Art

Diaphragm-type ultrasonic sensors are conventionally known. In this typeof ultrasonic sensor, a PZT ceramic thin film layer flanked by twoelectrodes is formed on one side of a diaphragm, and the electricalsignals output from the electrodes are used to detect ultrasonic waves(see, for example, Japanese Laid-Open Patent Application 2006-319945).

In the ultrasonic sensor in Patent Document 1, buckling caused byinternal stress of the diaphragm, which has a multi-layered film, isexploited to apply pressure in the upper direction of the diaphragm,thereby statically deflecting the diaphragm so that the diaphragmbecomes convex in the upper direction.

SUMMARY

However, a problem with the conventional ultrasonic sensor noted aboveis that the stress for deflecting the diaphragm is difficult to controlbecause the diaphragm is deflected depending on the diaphragm filmformation conditions and the like, and the properties vary from sensorto sensor. Another problem is that the level of diaphragm deflectionvaries as the diaphragm temperature varies, resulting in unstableproperties. Yet another problem is that the transmission and receptionproperties are difficult to optimize because of changes in the shape ofthe diaphragm after the formation of the ultrasonic sensor.

According to various aspects of the present invention, an ultrasonictransducer, an ultrasonic transducer array, and an ultrasonic device areprovided in which the properties can be made uniform and stable and inwhich the ultrasonic wave transmission properties and receptionproperties can be easily optimized.

According to a first aspect, an ultrasonic transducer configured totransmit or receive ultrasonic waves, and the ultrasonic transducerincludes a vibrating member, and a piezoelectric member coupled to thevibrating member. The piezoelectric member includes a firstpiezoelectric part configured and arranged to be deformed by appliedvoltage to vibrate the vibrating member or configured and arranged to bedeformed by vibration of the vibrating member to produce a potentialdifference, and a second piezoelectric part configured and arranged tobe deformed by applied voltage to statically deflect the vibratingmember.

Here, the ultrasonic transducer is an element which converts receivedultrasonic waves into electrical signals, and/or converts inputelectrical signals into ultrasonic waves, and transmits the signals orwaves, and includes, for example, ultrasonic sensors and ultrasonictransmission elements.

Configuring the ultrasonic transducer in this way allows the level anddirection of the static deflection of the vibrating member (e.g., adiaphragm) to be controlled by voltage applied to the secondpiezoelectric part. It is thereby possible to make the ultrasonictransducer properties uniform and stable. The deflection of thevibrating member refers to two phenomena: the phenomenon of the elasticdeformation of the vibrating member (and first piezoelectric part), andthe phenomenon of the changes in the state of the stress in thevibrating member. That is, when the vibrating member is vibrated by thefirst piezoelectric part, the level of deflection (change in state ofstress) of the vibrating member or the direction of deflection(distribution of stress) of the vibrating member can be controlled bythe second piezoelectric part, thereby allowing the ultrasonicdirectionality or transmission properties of the ultrasonic transducerto be controlled. The level and direction of deflection of the vibratingmember can also be controlled by the second piezoelectric part tocontrol the vibrating state of the vibrating member produced by theultrasonic waves that are incident on the vibrating member, and tocontrol the potential difference produced by the deformation of thefirst piezoelectric part. It is thus possible to control the ultrasonicreception properties of the ultrasonic transducer.

According to the ultrasonic transducer of the first aspect, theproperties can thus be made uniform and stable, and the ultrasonictransmission and reception properties can be easily optimized.

In the ultrasonic transducer according to the second aspect, the firstpiezoelectric part and the second piezoelectric part may be integrallyformed with each other. The first piezoelectric part may be connected toa first electrode and the second piezoelectric part may be connected toa second electrode with the first electrode and the second electrodebeing separated from each other.

Configuring the ultrasonic transducer in this way allows differentvoltage to be applied to the first and second piezoelectric parts, andallows the first and second piezoelectric parts to be drivenindependently. In addition, the potential difference produced by thefirst piezoelectric part can be detected by means of vibration of thevibrating member while the vibrating member is statically deflected bythe second piezoelectric part. The piezoelectric member can also beeasily manufactured, ultrasonic transducer productivity can be improved,and the manufacturing costs of the ultrasonic transducer can be reduced.

The ultrasonic transducer according to a third aspect further includes abase having an opening. The vibrating member may cover the opening ofthe base. The first and second piezoelectric parts may be disposed onone side of the vibrating member opposite from the base. The first andsecond piezoelectric parts may be disposed in an oscillation region thatoverlaps the opening of the base when viewed in a directionperpendicular to a main surface of the vibrating member.

Configuring ultrasonic transducer in this way allows the vibratingmember to be supported by the base and allows only the oscillationregion of the vibrating member to be vibrated. The natural frequency ofthe vibrating member in the oscillation region can also be adjusteddepending on the size and shape of the opening. It is also possible tovibrate the oscillation region of the vibrating member by means of thefirst piezoelectric part or to deform the first piezoelectric part bymeans of the vibration of the oscillation region of the vibrating memberwhile the oscillation region of the vibrating member is staticallydeflected by the second piezoelectric part.

In the ultrasonic transducer according to a fourth embodiment, the firstpiezoelectric part may be disposed in a center portion of theoscillation region, and the second piezoelectric part may be disposed onthe periphery of the first piezoelectric part.

Configuring the ultrasonic transducer in this way allows thecircumference of the vibrating member to be deformed by the secondpiezoelectric part and allows the vibrating member in the oscillationregion to be deflected in a convex or concave manner on the base side.The convexly or concavely deflected vibrating member can be vibrated bythe first piezoelectric part, or the first piezoelectric part can bedeformed by the vibration of the convexly or concavely deflectedvibrating member.

In the ultrasonic transducer according to a fifth aspect, the secondpiezoelectric part may be disposed adjacent to a boundary of theoscillation region.

Configuring the ultrasonic transducer in this way allows the areabordering the oscillation region of the vibrating member to be deformedand allows the oscillation region of the vibrating member to be moreefficiently deflected convexly or concavely on the base side.

In the ultrasonic transducer according to a sixth aspect, the secondpiezoelectric part may include a plurality of piezoelectric components.

Configuring the ultrasonic transducer in this way allows the deformedstate of the individual second piezoelectric parts to be varied andallows the oscillation region to be deformed into a desired shape.

The ultrasonic transducer array according to a seventh aspect includes aplurality of the ultrasonic transducers according to any of the aspectsdescribed above.

Configuring the ultrasonic transducer array in this way allows theultrasonic transducer properties provided to the ultrasonic transducerarray to be made uniform and stable and allows the ultrasonictransmission and reception properties to be easily optimized.

Therefore, according to the ultrasonic transducer array according to theseventh aspect, the ultrasonic transducer array properties can be madeuniform and stable, and the ultrasonic transmission and receptionproperties can be easily optimized.

The ultrasonic device according to an eighth aspect includes theultrasonic transducer or the ultrasonic transducer array according toany of the above aspects, and includes a control unit configured tocontrol input signals input to the ultrasonic transducer and to processoutput signals output from the ultrasonic transducer.

Configuring the ultrasonic device in this way allows ultrasonic waves tobe transmitted by any ultrasonic transducer and allows ultrasonic wavesto be received by the other ultrasonic transducers. Additionally, afterultrasonic waves have been transmitted by individual ultrasonictransducers, ultrasonic waves reflected on an object that is to bedetected can be detected by individual ultrasonic transducers.

In the ultrasonic device according to the ninth aspect, the control unitmay have a first control part configured to control the voltage appliedto the first piezoelectric part and to process the potential differenceproduced by the first piezoelectric part, and a second control partconfigured to control the voltage applied to the second piezoelectricpart.

Configuring the ultrasonic device in this way allows the first andsecond controllers to be independently operated and allows the first andsecond piezoelectric parts to be independently controlled.

In the ultrasonic device according to a tenth aspect, the first controlpart and the second control part may be configured to be controlledindependently from each other.

Configuring the ultrasonic device in this way allows the voltage appliedto the second piezoelectric part to be controlled by the secondcontroller according to the potential difference of the firstpiezoelectric part processed by the first controller, and allows voltageapplied to the first piezoelectric part to be controlled according tothe voltage applied to the second piezoelectric part.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a perspective view of a PDA in a first embodiment of thepresent invention;

FIG. 2 is a perspective view of an ultrasonic transducer array andultrasonic transducer device in the first embodiment of the presentinvention;

FIG. 3 is a system configuration diagram of the controllers of theultrasonic transducer array device shown in FIG. 2;

FIG. 4 is a cross sectional view of an ultrasonic transducer along lineA-A′ in FIG. 2;

FIG. 5 is a plan of the bottom electrode of the ultrasonic transducershown in FIG. 4;

FIGS. 6( a) and 6(b) are cross sectional views in which the diaphragm ofthe ultrasonic transducer shown in FIG. 4 is shown while deflected;

FIG. 7 is a plan of the bottom electrode of the ultrasonic transducer ina second embodiment of the present invention;

FIG. 8 is a cross sectional view of the ultrasonic transducer in thesecond embodiment of the present invention;

FIGS. 9( a) and 9(b) are cross sectional views in which the diaphragm ofthe ultrasonic transducer shown in FIG. 8 is shown while deflected; and

FIGS. 10( a) and 10(b) are cross sectional views showing variants of theultrasonic transducer shown in FIG. 2.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A first embodiment of the present invention is illustrated below withreference to drawings. In the following figures, the scale of the layersand members has been modified as needed to ensure that each layer andmember is large enough to be seen in the figures.

FIG. 1 is a perspective view schematically representing the structure ofa PDA (Personal Data Assistant) 100 in the present embodiment. FIG. 2 isan exploded perspective view schematically representing the structure ofan ultrasonic device 50 provided to the PDA 100 in the presentembodiment. FIG. 3 is a system configuration diagram schematicallyrepresenting the structure of the controller 40 (control unit) of theultrasonic device 50 in the present embodiment. FIG. 3 does not show thestructure for applying constant voltage to the second bottom electrodedescribed below.

As shown in FIG. 1, the main body 30 of the PDA 100 in the presentembodiment has a display 20. The display 20 is composed, for example, ofa liquid crystal panel or organic EL panel, is connected to acomputer/controller housed inside the main body 30, and displays variousoperating images or other data. An ultrasonic device 50 is provided onthe circumference of the main body 30. The ultrasonic device 50functions as an input device that detects the configuration or operationof a human hand, finger, or input pen, for example, for input to the PDA100.

As shown in FIG. 2, the ultrasonic device 50 has a base 11 in which aplurality of openings 11 a is formed in an array. The base 11 is formedfrom a single crystal silicon substrate, for example. An ultrasonictransducer 1 is provided in each opening 11 a. That is, the ultrasonictransducer array 10 is configured so as to have a plurality ofultrasonic transducers 1 disposed in an array on one side of the base11. The ultrasonic device 50 also has a controller 40 for controllingthe ultrasonic transducer array 10.

Wires (not shown) are connected to each of the individual ultrasonictransducers 1, and each wire is connected to a terminal 13 a on acontrol board 13 via a flexible printed board 12 connected to the base11. The controller 40, which is composed of a computer, memory, and thelike, is provided to the control board 13. The controller 40 is composedin such a way as to control input signals input to the ultrasonictransducers 1 and to process output signals output from the ultrasonictransducers 1.

As shown in FIG. 3, the controller 40 is connected to the ultrasonictransducer array 10, and is primarily equipped with a control/computingunit 41, memory 42, ultrasonic generator 43, ultrasonic detector 44, andT/R switch 45 for switching between transmission and reception. Theultrasonic generator 43 is composed of a sine wave generator 43 a forgenerating sine waves, a phase shifter 43 b that is provided for theindividual ultrasonic transducers 1 and that changes the phase of sinewaves, and a driver 43 c. The ultrasonic detector 44 is composedprimarily of an amplifier 44 a and an A/D converter 44 b.

In the control/computing unit 41, sine waves are generated by the sinewave generator 43 a during ultrasonic emission by the ultrasonictransducer array 10, and the phase shifter 43 b changes the sine wavesto phases corresponding to the individual ultrasonic transducers 1. Whenan ultrasonic wave is received by the ultrasonic transducer array 10,the control/computing unit 41 also switches the T/R switch 45 and sendsoutput signals output from the ultrasonic transducer array 10 to theamplifier 44 a. The control/computing unit 41 is also configured so asto be capable of outputting data stored in the memory 42 to thecontrol/computing unit (not shown) of the PDA 100. The control/computingunit 41 also has a first controller 41 a (first control part) and asecond controller 41 b (second control part).

FIG. 4 is an enlarged cross sectional view in which the ultrasonictransducer array 10 shown in FIG. 2 is cut along line A-N, and oneultrasonic transducer 1 is enlarged. FIG. 5 is a plan of the bottomelectrode of the ultrasonic transducer 1. The cross sectional view ofFIG. 4 also corresponds to the cross section along line B-B′ in FIG. 5.

In FIG. 2, the shape of the openings 11 a provided in the base 11 isrepresented in the form of squares, as viewed in a plane, but in thefollowing description, the shape of the openings 11 a will be round, asviewed in a plane.

The ultrasonic transducer 1 in the embodiment shown in FIG. 4 is anultrasonic transducer that transmits or receives ultrasonic waves. Theultrasonic transducer 1 has a base 11 in which an opening 11 a isformed, a diaphragm 2 (vibrating member) provided so as to block theopening 11 a of the base 11, a piezoelectric member 3 provided on theother side of the diaphragm 2 from the base 11, and a bottom electrode 4and top electrode 5 connected to the piezoelectric member 3.

The opening 11 a formed in the base 11 has a depth of about 180 μm to200 μm, for example.

The diaphragm 2 has a two-layered structure comprising a first oxidefilm 2 a formed with SiO₂, for example, that is provided on the base 11side, and a second oxide film 2 b formed with ZrO₂, for example, that islaminated on the other side of the first oxide film 2 a from the base11. The first oxide film 2 a is formed to a thickness of about 3 μm bythermal oxidation of the surface of a single-crystal silicon substrate,for example. The second oxide film is formed to a thickness of about 400nm, for example, by CVD (chemical vapor deposition), for example.

The region where the diaphragm 2 overlaps the opening 11 a when viewedin a direction perpendicular to a main surface of the diaphragm 2, andis exposed to the opening 11 a is the oscillation region V of thediaphragm 2. The diameter D of the opening 11 a is set as needed withinthe range of about 100 μm to hundreds of micrometers, for example,according to the natural frequency of the diaphragm 2 in the oscillationregion V.

The bottom electrode 4 is provided in the oscillation region V on theother side of the diaphragm 2 from the base 11.

As shown in FIG. 4 and FIG. 5, the bottom electrode 4 is divided into afirst bottom electrode (first electrode) 4 a provided in the center ofthe oscillation region V and a second bottom electrode (secondelectrode) 4 b provided therearound. The first bottom electrode 4 a andsecond bottom electrode 4 b are connected to wires 6 a and 6 b, each ofwhich is connected to the controller 40 of the ultrasonic transducerarray 10. The bottom electrode 4 is formed to a thickness of about 200nm using a conductive metal material such as Ir. The piezoelectricmember 3 is provided on the bottom electrode 4 in the oscillation regionV and outside the boundary thereof so as to cover the bottom electrode4.

The piezoelectric member 3 is formed with PZT (lead zirconate titanate)or BaTiO₃ (barium titanate), for example, and is composed of a firstpiezoelectric part 3 a in the center and a second piezoelectric part 3 btherearound. In other words, the piezoelectric member 3 is integrallyformed, and the first bottom electrode 4 a and second bottom electrode 4b are separated from each other, so that the portion of thepiezoelectric member 3 corresponding to the first bottom electrode 4 ais the first piezoelectric part 3 a, and the portion of thepiezoelectric member 3 corresponding to the second bottom electrode 4 bis the second piezoelectric part 3 b.

The first piezoelectric part 3 a is the middle portion of thepiezoelectric member 3 connected to the first bottom electrode 4 a. Thefirst piezoelectric part 3 a is for vibrating the diaphragm 2 upon beingdeformed by applied voltage, or for producing potential difference uponbeing deformed by the vibration of the diaphragm 2.

The second piezoelectric part 3 b is the circumferential portion of thepiezoelectric member 3 connected to the second bottom electrode 4 b. Thesecond piezoelectric part 3 b is deformed by applied voltage tostatically deflect the diaphragm 2. The second piezoelectric part 3 b isprovided near the boundary of the oscillation region V so as to straddlethe boundary of the oscillation region V.

The top electrode 5 is formed on top of the piezoelectric member 3. Thetop electrode 5 is formed with a conductive metal material such as Ir,and is connected to the first piezoelectric part 3 a and secondpiezoelectric part 3 b. The thickness of the top electrode 5 is about 50nm, for example. The top electrode 5 is connected via a wire 7 to thecontroller 40 of the ultrasonic transducer array 10.

The first controller 41 a of the control/computing unit 41 shown in FIG.3 is configured so as to control the ultrasonic generator 43 and T/Rswitch 45 to control the voltage applied to the first piezoelectric part3 a of the individual ultrasonic transducers 1 (see FIG. 4) provided tothe ultrasonic transducer array 10. The first controller 41 a is alsoconfigured so as to control the T/R switch 45, ultrasonic detector 44,and memory 42 shown in FIG. 3 to process the potential differenceproduced by the first piezoelectric part 3 a shown in FIG. 4.

The second controller 41 b of the control/computing unit 41 shown inFIG. 3 is configured so as to control the T/R switch 45 to control thevoltage applied to the second piezoelectric part 3 b of the individualultrasonic transducers 1 (see FIG. 4) provided to the ultrasonictransducer array 10.

The control/computing unit 41 shown in FIG. 3 is also configured so asto be capable of independently controlling the first controller 41 a andsecond controller 41 b.

The operation of the present embodiment is described next.

As shown in FIG. 1, ultrasonic waves are generated by the ultrasonicdevice 50 in the detection region when the PDA 100 detects theconfiguration or operation of a human hand or finger.

First, the controller 40 of the ultrasonic device 50 applies constantvoltage across the top electrode 5 and second bottom electrode 4 b oftransmitting ultrasonic transducers 1. Specifically, the secondcontroller 41 b shown in FIG. 3 controls the T/R switch 45 to applyconstant voltage across the top electrode 5 and second bottom electrode4 b of the transmitting ultrasonic transducers 1 (see FIG. 4) providedto the ultrasonic transducer array 10. When voltage is applied acrossthe top electrode 5 and second bottom electrode 4 b, the secondpiezoelectric part 3 b that has been formed so as to straddle theboundary of the oscillation region V of the diaphragm 2 as shown in FIG.4 is elongated or compressed in the planar direction of the diaphragm 2according to the applied voltage.

When the second piezoelectric part 3 b is elongated in the planardirection of the diaphragm 2, the piezoelectric member 3 side of thediaphragm 2 is elongated in the planar direction near the boundary ofthe oscillation region V of the diaphragm 2, and the oscillation regionV of the diaphragm 2 becomes convex (convex in the downward direction inthe figure) on the base 11 side as shown in FIG. 6( a). When the secondpiezoelectric part 3 b is compressed in the planar direction of thediaphragm 2, the piezoelectric member 3 side of diaphragm 2 iscompressed in the planar direction near the boundary of the oscillationregion V of the diaphragm 2, and the oscillation region V of thediaphragm 2 becomes concave (convex in the upward direction in thefigure) on the base 11 side as shown in FIG. 6( b).

In this way, the voltage applied to the second piezoelectric part 3 b ofthe individual ultrasonic transducers 1 is controlled so that the leveland direction of the static deflection of the diaphragms 2 of thevarious transmitting and receiving ultrasonic transducers 1 arecontrolled as desired. Here, the deflection of the diaphragm 2 includesnot only the phenomenon of the elastic deformation of the diaphragm 2but also the phenomenon of the changes in the state of the diaphragm 2stress. The voltage applied to the second piezoelectric parts 3 b of thevarious ultrasonic transducers 1 is also kept constant to maintain thestatic deflection of the oscillation region V of the diaphragm 2 in thedesired configuration.

Next, while the oscillation region V of the diaphragm 2 is staticallydeflected, the first controller 41 a of the controller 40 as shown inFIG. 3 controls the sine wave generator 43 a to generate sine waves, andapplies sine wave voltage, which is phase-shifted a little at a time, tothe first bottom electrode 4 a of each of the ultrasonic transducers 1of the ultrasonic transducer array 10 via the phase shifter 43 b, driver43 c, and T/R switch 45. The first piezoelectric parts 3 a of theultrasonic transducers 1 thus expand and contract in the planardirection of the diaphragms 2, and the oscillation regions V of thediaphragms 2 vibrate in the normal direction of the diaphragms 2.

Here, sine wave voltage that is phase-shifted a little at a time isapplied to the first bottom electrode 4 a of each of the ultrasonictransducers 1. The diaphragm 2 in the oscillation region V of each ofthe ultrasonic transducers 1 thus vibrates while phase-shifted a littleat a time.

The diaphragm 2 in the oscillation region V of each of the ultrasonictransducers 1 vibrates while phase-shifted a little at a time, causinginterference in the ultrasonic waves generated by the ultrasonictransducers 1. Due the interference of the ultrasonic waves generated bythe ultrasonic transducers 1, the direction in which the ultrasonicwaves travel becomes inclined in the normal direction of the diaphragm2, imparting directionality to the ultrasonic waves.

At this time, the control frequency of the sine wave voltage applied tothe first piezoelectric part 3 a through the control of the ultrasonicgenerator 43 by the first controller 41 a of the controller 40 is about100 kHz, for example, and the amplitude is about 10 V. The potentialdifference of the sine wave voltage applied to the ultrasonictransducers 1 is about 0.5 μs, for example. The voltage (DC potential)applied to the second piezoelectric part 3 b through the control of theT/R switch 45 by the second controller 41 b of the controller 40 is alsoabout 5 V, for example.

This change in the ultrasonic wave directionality is exploited and theshift in the phase of the sine wave voltage applied to the firstpiezoelectric parts 3 a of the ultrasonic transducers 1 is changed tothereby change the direction of the ultrasonic waves generated by theultrasonic transducer array 10 of the ultrasonic device 50 shown in FIG.1 and to scan the detection region of the PDA 100.

At this time, when a human hand or finger, for example, is present inthe detection region as shown in FIG. 1, the ultrasonic waves generatedby the ultrasonic transducer array 10 are reflected by the human hand orfinger. When the ultrasonic waves reflected by the human hand or fingerreach the receiving ultrasonic transducers 1 of the ultrasonictransducer array 10, the oscillation regions V of the diaphragms 2 ofthe ultrasonic transducers 1 vibrate. When the oscillation regions V ofthe diaphragms 2 vibrate, the first piezoelectric parts 3 a expand andcontract with the expansion and contraction in the planar direction ofthe diaphragms 2, and the first piezoelectric parts 3 a produce apotential difference.

The potential difference produced by the first piezoelectric parts 3 ais transmitted in the form of output signals from the ultrasonictransducers 1 to the ultrasonic transducer array 10 by the wiring 6 aand 7 connected to the top electrodes 5 and first bottom electrodes 4 a.The output signals from the individual ultrasonic transducers 1 to thecontroller 40 of the ultrasonic transducer array 10 are stored in thememory 42 via the T/R switch 45, amplifier 44 a, and A/D converter 44 b.The first controller 41 a of the control/computing unit 41 calculatesand outputs the distance to the human hand or finger in the detectionregion and the moving speed based on the output signals from theultrasonic transducers 1 stored in the memory 42.

The hand or finger state and movement are recognized by the computercontroller (not shown) of the PDA 100 based on the distance to the humanhand or finger and the moving speed input by the ultrasonic transducerarray 10, and are compared to pre-registered finger or hand states andmovements. If the results of comparison reveal the detected human handor finger state and movement to be consistent with those that have beenpre-registered, the computer controller of the PDA 100 recognizes thehuman hand or finger configuration or movement as prescribed input andimplements a prescribed pre-registered operation such as the display ofan image on the display 20, for example.

According to the PDA 100 of the present embodiment, the ultrasonictransducer array 10 can thus function as an input device.

Here, the piezoelectric members 3 of the ultrasonic transducers 1provided to the ultrasonic transducer array 10 are composed of firstpiezoelectric parts 3 a and second piezoelectric parts 3 b. The leveland direction of the static deflection of the diaphragms 2 can thereforebe controlled by the voltage (DC potential) applied to the secondpiezoelectric parts 3 b. Thus, when ultrasonic waves are generated uponthe vibration of the diaphragms 2 by the first piezoelectric parts 3 ato which sine wave voltage has been applied, the level and direction ofthe deflection of the diaphragms 2 can be controlled by the secondpiezoelectric parts 3 b to which the DC potential voltage has beenapplied, and the ultrasonic wave directionality or transmissionproperties of the ultrasonic transducers 1 can be controlled.

The level and direction of deflection in the diaphragm 2 can also becontrolled by the second piezoelectric part 3 b to control the state ofvibration produced in the diaphragm 2 by the ultrasonic waves incidenton the oscillation region V of the diaphragm 2 and to adjust the inputsignals by changing the voltage produced upon the deformation of thefirst piezoelectric part 3 a. It is thus possible to control theultrasonic sensitivity and reception properties of the ultrasonictransducers 1.

The diaphragm 2 can also be deflected so as to result in a concave shapeon the base 11 side as shown in FIG. 6( b) to thereby focus theultrasonic waves generated by the vibration of the diaphragm 2 and toadjust the ultrasonic wave intensity or distance.

In addition, in the ultrasonic transducer 1 of the present embodiment,the first piezoelectric part 3 a and second piezoelectric part 3 b areintegrated with each other, and the first bottom electrode 4 a andsecond bottom electrode 4 b are separated from each other. It is thuspossible to apply different voltages to the first piezoelectric part 3 aand second piezoelectric part 3 b, and to allow the first piezoelectricpart 3 a and second piezoelectric part 3 b to be independently driven.In addition, the potential difference produced by the firstpiezoelectric part 3 a can be detected by means of the diaphragm 2vibration while the diaphragm 2 is statically deflected by the secondpiezoelectric part 3 b. The piezoelectric member 3 can also be easilymanufactured, the ultrasonic transducer 1 productivity can be improved,and the manufacturing costs of the ultrasonic transducer 1 and theultrasonic transducer array 10 can be reduced.

The diaphragm 2 of the ultrasonic transducer 1 in the present embodimentis also provided in such a way as to block the opening 11 a of the base11, and the first piezoelectric part 3 a and second piezoelectric part 3b are provided in the oscillation region V of the diaphragm 2. Thediaphragm 2 can thus be supported by the base 11, and only theoscillation region V of the diaphragm 2 will vibrate. The naturalfrequency of the diaphragm 2 in the oscillation region V can also beadjusted depending on the size and shape of the openings 11 a. It isalso possible to vibrate the oscillation region V of the diaphragm 2 bymeans of the first piezoelectric part 3 a or to deform the firstpiezoelectric part 3 a by means of the vibration of the oscillationregion V of the diaphragm 2 while the oscillation region V of thediaphragm 2 is statically deflected by the second piezoelectric part 3b.

In the ultrasonic transducer 1 of the present embodiment, the firstpiezoelectric part 3 a is provided in the center of the oscillationregion V, and the second piezoelectric part 3 b is provided around thefirst piezoelectric part 3 a. The circumference of the oscillationregion V of the diaphragm 2 can thus be deformed by the secondpiezoelectric part 3 b, and the diaphragm 2 in the oscillation region Vcan be convexly or concavely deflected on the base 11 side. The convexlyor concavely deflected diaphragm 2 can be vibrated by the firstpiezoelectric part 3 a, or the first piezoelectric part 3 a can bedeformed by the vibration of the convexly or concavely flexed diaphragm2.

In the ultrasonic transducer 1 in the present embodiment, the secondpiezoelectric part 3 b is also provided near the boundary of theoscillation region V. The diaphragm 2 can thus be deformed in thevicinity of the oscillation region V, and the oscillation region V ofthe diaphragm 2 can be more efficiently deflected convexly or concavelyon the base 11 side.

The ultrasonic device 50 of the present embodiment also has a controller40 for controlling input signals input to the ultrasonic transducers 1and for processing output signals output from the ultrasonic transducers1. This makes it possible to control the frequency or acoustic pressureof the ultrasonic waves generated by the ultrasonic transducers 1. It isalso possible to detect and measure ultrasonic waves received by theultrasonic transducers 1.

In the ultrasonic device 50 of the present embodiment, the controller 40also has a first controller 41 a for controlling the voltage applied tothe first piezoelectric part 3 a and for processing the potentialdifference produced by the first piezoelectric part 3 a, and a secondcontroller 41 b for controlling the voltage applied to the secondpiezoelectric part 3 b. The first controller 41 a and second controller41 b can thus be independently operated, and the first piezoelectricpart 3 a and second piezoelectric part 3 b can be independentlycontrolled. The frequencies of the individual transducers 1 can thus becontrolled, and variation between the transducers 1 of the transducerarray 10 can be corrected.

In the ultrasonic device 50 of the present embodiment, the firstcontroller 41 a and second controller 41 b are configured to allowindependent control. The voltage applied to the second piezoelectricpart 3 b can thus be controlled by the second controller 41 b accordingto the potential difference of the first piezoelectric part 3 aprocessed by the first controller 41 a, and the voltage applied to thefirst piezoelectric part 3 a can be controlled according to the voltageapplied to the second piezoelectric part 3 b.

For example, feedback control can be implemented, wherein computingfunctions can be performed by the control/computing unit 41 based ondata for ultrasonic waves detected by the first controller 41 a, and theresults can be reflected in controlling the voltage applied to thesecond piezoelectric part 3 b by the second controller 41 b.

As described above, according to the ultrasonic device 50 equipped withthe ultrasonic transducer 1 and ultrasonic transducer array 10 of thepresent embodiment, the sensing properties can be made uniform andstable, and the ultrasonic transmission and reception properties can beeasily optimized. Input to the PDA 100 can thus be achieved withoutcontact, and the input can be done easily and reliably.

Second Embodiment

A second embodiment of the present invention is described below withreference to FIGS. 1 through 3, 7, and 8. The ultrasonic transducer 1Ain the present embodiment is different from the ultrasonic transducer 1described in the first embodiment above in that the transducer has aplurality of second bottom electrodes 4 b 1 through 4 b 4, and also hasa plurality of second piezoelectric components 3 b 1 through 3 b 4corresponding to the second bottom electrodes 4 b 1 through 4 b 4. Theembodiment is the same as the first embodiment in other respects, andthe same parts will therefore be identified by the same symbols withoutfurther elaboration.

FIG. 7 is a plan view of the bottom electrode 4A of the ultrasonictransducer 1A in the present embodiment, corresponding to FIG. 5 in thefirst embodiment. FIG. 8 is an enlarged cross sectional view of theultrasonic transducer 1A in the present embodiment, corresponding toFIG. 4 in the first embodiment. Here, FIG. 8 is a cross sectional viewcorresponding to the cross section along line C-C′ in FIG. 7.

As shown in FIG. 7, in the ultrasonic transducer 1A of the presentembodiment, a first bottom electrode 4 a is provided in the center ofthe oscillation region V of the diaphragm 2 and is connected by a wire 6a to the controller 40. A plurality of second bottom electrodes 4 b 1through 4 b 4 is formed around the first bottom electrode 4 a. Thesecond bottom electrodes 4 b 1 through 4 b 4 are each connected by wires6 b 1 through 6 b 4, respectively, to the controller 40. The secondbottom electrodes 4 b 1 through 4 b 4 are also formed near the boundaryof the oscillation region V of the diaphragm 2 so as to straddle theboundary.

As shown in FIG. 8, the portions flanked by the second bottom electrodes4 b 1 through 4 b 4 and the top electrode 5 are second piezoelectriccomponents 3 b 1 through 3 b 4 in the present embodiment. That is, theultrasonic transducer 1A in the present embodiment has a plurality ofsecond piezoelectric components 3 b 1 through 3 b 4 corresponding to theplurality of second bottom electrodes 4 b 1 through 4 b 4.

The operation of the present embodiment is described next.

The incline of the oscillation region V of the diaphragm 2 can bereversed, as shown in FIG. 9( b), when the second piezoelectriccomponent 3 b 2 is elongated in the planar direction of the diaphragm 2as voltage is applied across the top electrode 5 and second bottomelectrode 4 b 2, and the second piezoelectric component 3 b 4 iscompressed in the planar direction of the diaphragm 2 as voltage isapplied across the top electrode 5 and the second bottom electrode 4 b4. Similarly, no voltage is applied to the second bottom electrode 4 b 1and second bottom electrode 4 b 3 at this time.

In this way, the incline direction and angle of the oscillation region Vof the diaphragm 2 can be freely controlled within a prescribed range byselecting the second piezoelectric components 3 b 1 through 3 b 4 towhich voltage is applied and by controlling the DC voltage applied tothe individual second piezoelectric components 3 b 1 through 3 b 4. Itis thus possible to more freely change the ultrasonic transmission andreception directions, and to more easily optimize the properties of theindividual ultrasonic transducers 1. The frequencies of the individualtransducers 1 can thus be controlled, and variation between thetransducers 1 of the ultrasonic transducer array 10 can be corrected.

Variants of the ultrasonic transducer 1 described in the firstembodiment above are described below.

FIGS. 10( a) and 10(b) are enlarged cross sectional views, correspondingto FIG. 4 of the first embodiment, which show variants of the ultrasonictransducer 1.

As shown in FIG. 10( a), the first piezoelectric part 3 a and secondpiezoelectric part 3 b are separately formed in addition to the bottomelectrode 4 in the ultrasonic transducer 1 described in the firstembodiment. In addition, an ultrasonic transducer 1B may be formed byseparating the top electrode 5 in correspondence to the firstpiezoelectric part 3 a and second piezoelectric part 3 b.

This will allow the first piezoelectric part 3 a and secondpiezoelectric part 3 b to be driven completely independently of eachother, and will allow each to be operated independently. It is thuspossible to prevent the sensing and oscillation of the firstpiezoelectric part 3 a from unnecessarily affecting the expansion andcontraction of the second piezoelectric part 3 b.

As shown in FIG. 10( b), an ultrasonic transducer 1C may be formed byintegrally forming the bottom electrode 4 in the ultrasonic transducer 1described in the first embodiment, and separating the top electrode 5into a first top electrode 5 a and second top electrode 5 b incorrespondence to the first piezoelectric part 3 a and secondpiezoelectric part 3 b. This can provide the same effects as theultrasonic transducer 1 of the first embodiment.

The present invention is not limited to the embodiments above, andvarious changes can be made without departing from the scope of theinvention. For example, the planar shape of the openings formed in thebase is not limited to square or round shapes.

Also, the second piezoelectric part may be provided in the center of theoscillation region of the diaphragm, and the first piezoelectric partmay be provided around the second piezoelectric part.

The bottom electrode provided near the boundary of the oscillationregion of the diaphragm may also be provided on the outside of theboundary in such a way that the end overlaps the boundary, and may beprovided on the inside of the boundary in such a way that the endoverlaps the boundary. The electrode may also be provided inside oroutside the oscillation region, without the end overlapping theboundary.

The first piezoelectric part may also be divided into a plurality ofcomponents.

The individual ultrasonic transducers of the ultrasonic transducer arraymay also both transmit and receive, without being divided into those fortransmission and those for reception.

The PDA may also have a plurality of ultrasonic transducer arrays.

An ultrasonic device having a plurality of ultrasonic transducers wasdescribed in the embodiments above, but needless to say, the presentinvention is also applicable to ultrasonic devices composed of a singleultrasonic transducer and controller.

General Interpretation of Terms

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts. Finally, terms of degree such as“substantially”, “about” and “approximately” as used herein mean areasonable amount of deviation of the modified term such that the endresult is not significantly changed. For example, these terms can beconstrued as including a deviation of at least ±5% of the modified termif this deviation would not negate the meaning of the word it modifies.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

1. An ultrasonic transducer configured to transmit or receive ultrasonicwaves, the ultrasonic transducer comprising: a vibrating member; and apiezoelectric member coupled to the vibrating member, the piezoelectricmember including a first piezoelectric part configured and arranged tobe deformed by applied voltage to vibrate the vibrating member orconfigured and arranged to be deformed by vibration of the vibratingmember to produce a potential difference, and a second piezoelectricpart configured and arranged to be deformed by applied voltage tostatically deflect the vibrating member.
 2. The ultrasonic transduceraccording to claim 1, wherein the first piezoelectric part and thesecond piezoelectric part are integrally formed with each other, thefirst piezoelectric part being connected to a first electrode and thesecond piezoelectric part being connected to a second electrode with thefirst electrode and the second electrode being separated from eachother.
 3. The ultrasonic transducer according to claim 1, furthercomprising a base having an opening, the vibrating member covering theopening of the base, and the first and second piezoelectric parts beingdisposed on one side of the vibrating member opposite from the base, thefirst and second piezoelectric parts being disposed in an oscillationregion that overlaps the opening of the base when viewed in a directionperpendicular to a main surface of the vibrating member.
 4. Theultrasonic transducer according to claim 3, wherein the firstpiezoelectric part is disposed in a center portion of the oscillationregion, and the second piezoelectric part is disposed on the peripheryof the first piezoelectric part.
 5. The ultrasonic transducer accordingto claim 3, wherein the second piezoelectric part is disposed adjacentto a boundary of the oscillation region.
 6. The ultrasonic transduceraccording to claim 1, wherein the second piezoelectric part includes aplurality of piezoelectric components.
 7. An ultrasonic transducer arrayincluding a plurality of the ultrasonic transducers according toclaim
 1. 8. An ultrasonic device comprising: the ultrasonic transduceraccording to claim 1; and a control unit configured to control inputsignals input to the ultrasonic transducer and to process output signalsoutput from the ultrasonic transducer.
 9. The ultrasonic deviceaccording to claim 8, wherein the control unit has a first control partconfigured to control the voltage applied to the first piezoelectricpart and to process the potential difference produced by the firstpiezoelectric part, and a second control part configured to control thevoltage applied to the second piezoelectric part.
 10. The ultrasonicdevice according to claim 9, wherein the first control part and thesecond control part are configured to be controlled independently fromeach other.